Question: Some squirrels were sitting on a branch. $6$ more squirrels joined them. Now, there are $11$ squirrels on the branch. How many squirrels were on the branch at first?
Solution: $ \begin{aligned}&{?} \text{ squirrels}\\ +&\underline{ {6} \text{ squirrels joined them}}\\ =&{11} \text{ squirrels on the branch}\end{aligned}$ $5$ squirrels